Continuous contact printer



C. O. ARL$ON ETAL counuuous counc'r Pnnvrnn I'illd June 10. 1964 Jan.17, 1967 Roller Prcssm Area. 44

'xasuref? ion p 46" f mf. ASFW/ l lnvenf Carl d Carlson Bnyhnin F. ScharUnited States Patent O 3,298,297 CONTINUOUS CONTACT PRINTER Carl 0.Carlson, Los Angeles, and Benjamin F. Scherf,

Hawthorne, Calif., assignors to The National Cash Register Company,Dayton, Uhio, a corporation of Maryland Filed June 10, 1964, Ser. No.374,120

Claims. (Cl. 95--77.5)

This invention relates to a photographic contact printer and, moreparticularly, to an improved contact printer for printing high-resolution images by establishing a high degree of contact between thesurfaces of a master negative and a film on which the images are to beprinted.

Microimages having an equivalent resolution of 1,000 lines permillimeter or better are readily produced using known techniques andapparatus, for example, as disclosed in a copending United Statesapplication Ser. No. 111,759, filed on May 22, 1961, now Patent No.3,185,026, inventors Carl O. Carlson et al., and assigned to' the sameassignee as this application. -Tbe copending patent application teachesthat very high resolution microimages can be formed by projection onto aphotomethachromic (hereinafter called photochromic) emulsion that iscoated on a glass plate. Also the copending application teaches thatpermanent copies of the microimages formed in the photochromic coatingcan be contact printed onto a high resolution, conventional photographicfilm by using a contact printer having a resilient or felt-like support.The resilient support provides for transmitting only a normal, evenlydistributed pressure to the interface between the two coatings therebytending to compensate for any non-flatness of the surfaces of theemulsion coatings which surface nnevenness is a property of emulsions,especially when supplied as coatings on films. While, with care, highresolution contact prints can thus be made vby using such a resilientsupport for the lm, when it is desired to more easily and consistentlycontact print arrays' of high resolution microimages onto conventionalphotographic film. a more convenient and reliable manner of obtaining ahigh degrec of intimate contact between the coatings is required. Sincethe degree of resolution in the contact print is related to the degreeof contact between coatings, the measure of uniformity of contact can benoted by inspecting the lack of or the number of light interferencefringes present at the interface of the coatings. The spacing betweencoatings is directly related to the number and spacing of fringesformed, and is further related to the unevenness of the tilm coating.Thus, optimum contact, i.e., perfect Contact, refers to the conditionexisting when no light interference fringes are formed over theinterface of the contact surfaces. It is to be noted that although acontact print with acceptable resolution could be produced when afewwidely spaced interference fringes are present, the contact prints aregreatly degraded when many fringes are present. It has been found thatthe fringe regions are produced when pockets of air have been capturedaround clumps of emulsion at the time initial contact was made, and thatthe fringes or thc fringe regions can be reduced by one or more of thesteps of applying more pressure to the contacting surfaces, removing airfrom between the surfaces before applying pressure, and/or waiting afterpressure is applied for any air that might be entrapped between thesurfaces to leak out or be absorbed by the material to thereby assurebetter contact before exposing the film. The first approach, that is theuse of more pressure to acquire more intimate contact. is impracticablebecause there is a tendency to break the'master plates as largerpressures are applied. The second approach, that is "ice the removal ofair-before applying pressure, requires a vacuum system which materiallycomplicates the design and which is better avoided if possible. Thethird approach, which is waiting for the bubbles of trapped air todissipate, while generally helpful, provides no guarantee that the timedelay will improve the contact, inasmuch as it could happen that anoptimum contact has been formed around the air pocket cutting ott' themeans for the air to escape. lt has also been suggested that a matchingrefractive index liquid be placed between master and copy to eliminatethe interference fringes or that a fine grit be placed therebetween tomake the `fringes so numerous as to be unresolvable. However,

this approach does not prevent the images from being. undercut bydiffused illumination or prevent diffraction effects with semi-specularor specular illumination from blurring the microimages at points wheremaster and copy fail to bc in optimum contact. It should thus be clearthat in order to transfer the maximum. amount of very fine-lineinformation from the master to the copy, optimum or near optimum contactshould be produced at the interface between coatings.

lt has been mentioned above that optimum contact is achieved between thetwo coatings when no interference fringes are noticeable at theinterface. 1t shouldV be noted that interference fringes are notnoticeable when the spacing between the coatings is less thanone-quarter wavelength or when the spacing is relatively large so as tomake the interference fringes unresolvable. However, when the spacing isbetween these two limits and a red light of narrow bandwidth is used toilluminate the coatings, light and dark patterns are alternately formed.ylt has thus been observed that acceptable high resolution is producedin contact prints when the spac ing between coatings is equal to no morethan four wavelengths, which spacing is measured by counting theinterference fringes from a region of optimum contact in the propermanner as each continuous dark area represents a fixed spacing betweencoatings. Acceptable high resolution in a contact print is accomplishedfor the p'urposes and intent of the present invention when a six pointtype font of characters which has been reduced about 200 diameters ontoa master, is contact printed onto a photographic tilm, and thecharacters recorded or printed in the contact prints can be resolvedwith proper viewing equipment, for example.

A primary object of this invention is thus to provide an improvedcontact printer that can make contact prints of microimages having ahigh resolution by rapidly establisbing optimum or near optimum contactbetween a master negative and a photographic film.

Another object of this invention is to provide a continuously operatingcontact printer comprising a resilient roller having a generallyspheroidal shape for bringing together the coatings of a photographicfilm and a master negative. Because of its shape, the roller initiallycontacts the film at the center of its line of travel, and graduallyincreases the contact pressure and thus widens the area of contacttoward the edges of the film as the roller rolls over the film, tothereby even-out the surface of the film in the region of contact inwhich exposure is to take p ace.

Still another object of this invention-is to provide an improved contactprinter that can make a high resolution contact print from a masternegative by moving the master Generally, the present invention comprisesa resilient roller that initially applies pressures at only a very smallarea on a photographic film so as to press it against a fmaster negativethat is rigidly supported by a transparent member. Since the initialcontact area is small, a very high pressure is produced, and the highpoints in the films coating are effectively squashed so that the valleysas well as the high points in the films coating are placed in intimatecontact with the coating on the master in a narrow region under theresilient roller. A suitably shaped light source focuses a narrowrectangularly shaped light beam through the transparent member towardthe bottom of the resilient roller. The narrow4 rectangularly shapedregion, illuminated by the light spot, extends along the surface of theroller, parallel lto the axis thereof. It should be noted that thisfeature enables the film to be exposed only in the region wherein theroller forces the film and master into maximum intimate contact. In thepreferred embodiment of the invention, this result is readilyaccomplished by forming the transparent member, for supporting themaster, into a large roller or drum. Then as the resilient roller rollsover andpresses the film against the master, the film and master advancebetween the rotating rollers and are forced into intimate contact in theregion of illumination, thereby providing the desired conditions forprinting the images from the master onto the film.

It should be noted that only a portion of the images on the master, theportion in the illuminated region, is

--being exposed or printed at any given instant of time.

By making the illuminated region relatively small, only a small contactarea is required. Thus, higher pressure contact can be made by theroller so as to ensure a high degree of contact between the master andthe film. As the master and film are carried through the region ofillumination all the images are printed on the film.

Other objects, advantages and features of the present invention willbecome apparent from consideration o f the following description whentaken in conjunction with the appended claims and the drawings, wherein:

FIG. 1 shows a contact print as produced on a photographic film by amaster negative containing over 1200 high resolution microimages;

FIG. 2 is a greatly enlarged pictorial 'view yof a frag- 4 ment of themaster negative and support therefor as used to print the contact printshown in FIG. 1;

FIG. 3 is an exaggerated enlarged section of 'a fragment of an unexposedflexible photographic film showing a typical emulsion clump or highpoint protruding above the normal surface of the emulsion coating;

FIG. 4 is a pictorial schematic of the high resolution contact printerin accordance with this invention; and

FIG. 5 is a view taken on line 5-5 of FIG. 4 in the direction of thearrows showing the region where the film and master are in intimatecontact.

Referring to the drawings, FIG. 1 shows one of the high resolutionContact prints of michoimages that is made in accordance with theteachings of this invention. -The contact print shown has an' arraycomprising 50 columns and 25 rows of high resolution microimages 12formed on a flexible photographic film. Each microimage 12 represents apage (5 x 8 inches) of a book which h as been reduced over 200diameters, for example. Such a reduction readily provides 32 microimagesto the inch in each row and microimages to the inch in each column.Thus, an array of over 1200 microimages can be formed within an areasmaller than 2 inches by 2 inches on the contact print, and theresolution of each microimage is sufficient so that the printing can beeasily and clearly readable when the mirooimages are enlarged by aviewer specially designed to handle such small microimages, such as theviewer disclosed in the commonly assigned copending patent applicationSerial No. 329,743, filed December 1l, i963, now U.S. Patent No.3,267,801.

The contact print shown in FIG. l is made from a master 16, a fragmentof which is shown greatly enlarged in FIG. 2. The master 16 contains anarray of microimages 17 which are of the same size as microimages 12.The resolution of the microimages 17 is sufficiently high to allow forsome degrading during the contact printing process. It is well knownthat there are a number of factors that contribute to degrading theresolution of a contact print, among others, these factors include thedegree of contact between coatings, the thickness of the coating, andthe type of light exposing the coatings. The master 16 includes atransparent substrate 18 coated with a photosensitive coating 19 onwhich the. microimages 17 are formed. It should be understood that boththe thickness of the substrate 18 and the thickness of the coating 19are shown exaggerated in the drawings. In actual practice, to record thehigh resolution images thethickness of the coating 19 should be verythin, preferably in the order of one mireon. However, commerciallyavailable high resolution films have coatings, such as coating 19, whichare approximately six microns thick. Therefore, the images arerestricted to the surface of the coating, penetrating the coating to adepth of the order of one micron. The thickness of the substrate can beany convenient thickness, for example a few thousandths of an inch toone quarter of an inch.

Copies of microimages that are to be generally disseminated and are toreceive a lot of handling should preferably 'be made on a exiblephotographic film, such as the contact print shown in FIG. 1. Referringto FIG. 3, there is shown an enlarged cross-section of a typical highresolution flexible photographic film 2l. The high resolution film 21has a flexible base made of, for example, cellulose acetate 22 coatedwith a silver halide emulsion coating 23. However, due to limitations inthe process of applying a silver halide coating on a cellulose acetatefilm, the surface of the resultant coating 23 is relatively unevenmaking it difficult to obtain a near perfect contact between coatingsduring the printing process. The thickness of coating 23 is showngreatly exaggerated in FIG. 3 in comparison to the thickness of thecellulose acetate base 22. The cellulose acetate 'base has a thikness ofabout microns, but the coating 23 thereon has been observed to havepeaks, for example, peak 24 formed by an emulsion clump, which may beprotruding several microns above the normal surface of the coating 23,which may have an average thickness of 6 microns. Peaks, like the peak24, are spaced irregularly in the coating 23. It becomes apparent,therefore, that, when the surface of th ecoating 19 on the master 16 ispressed against an uneven surface -forrned on the coating 23 bf the film2l, air pockets may be trapped in the valleys formed around the peak 24unless precaution is taken during contact printing to prevent this fromoccurring. Air pockets are detrimental in printing very high resolutionmicroimages because the emulsion coatings 19 and 23 are prevented frommaking optimum contact. As is well understood in the art, spacingbetween emulsion coatings during contact printing fon'ns diffractionpatterns and interference fringes when the film is exposed to light,resulting in a blurring of the microimages being printed. Since themicroimages represent greately reduced printed information, the airpockets could be large enough to blur out the words on half of a page,for example.

Referring to FIG. 4, there is shown a device that produces optimum ornear optimum contact between the emulsion coatings of the master and lmas required for high resolution contact printing. The contact printershown is of the continuous type wherein a strip of photographic film 21and a master 16 are squeezed together into intimate contact as theyadvance between two rollers 26 and 27. The roller 26 has a resilientcovering 28 made of, for example, hard rubber, having a larger diameterat the center than at the ends thus forming a segment of a spheroid. Theroller 26 is mounted on a rigid hub 29, which, in turn, is mounted on anaxle 31 that rotates within two 'bearings 32 and 33. Bearings 32 and 33are suitably mounted (by structure not shown) so Pda-u lthat anadjustment can be made to the mountings f the bearings to urge theroller 26 to have the desired pressure against the roller 27.

When the film 21 and the master 16 are initially disposed between therollers 26 and 27, the roller 26 initially contacts the film 21 in asmall area along the center line of its travel, urging th`e film 21against the master 16. In turn, the master is urged against thecylindrical glass wall 36. Since the area in contact is small, a largepressure is produced on the few high points or peaks which may exist inthe emulsion coating on the film 21 within the area in contact toflatten the clumps and form intimate contact between the coatings on thefilm 21 and master 16. As the roller 26 is rotated in the direction ofarrow 57 by a motor and gearing assembly 56, the film and master advancebetween the rotating rollers 26 and 27. The convex surface on theresilient covering 28, upon coming Y into contact with the film, yieldsto conform to the contour of the larger diameter cylindrical glass wall36. In

turn, the small area in contact Ibetween the film and master increasesoutwardly placing more of the film 21 into intimate contact with themaster 16. It should be noted that, as any given point on the filmadvances between the rollers 26 and 27, the pressure applied to thepoint increases until the point is located along the region 46 parallelto the axes of rotation of the rollers 26 and 27. When the film andmaster are disposed between the rollers 26 and 27 as shown in FIG. 4,the covering 28 is deformed to make contact with the film within anelongated roller pressure larea 44 (enclosed by the two dtted lines,PIG. 5) which is wider at the center than at the ends. The pressure atthe center of the area 44 is greater than at the edges, because'theportion of the resilient covering 28 at the center of area 44 yieldedmore than at the edges. Since a pressure gradient exists Within area 44,air bubbles have a tendency to be displaced toward the outer edges ofthe area, thereby aiding in the prevention of the formation of airpockets.

Since the degree of contact between the film and master can bedetermined by inspecting the interface with a red light, axle 31 can bemoved toward or away from roller 27 by suitable adjustment means until afew or no interference fringes are observed along the center portion ofthe elongated roller pressure area 44. When optimum or near optimumcontact is obtained, the bearings 32 and 33 can be fixed in place, and anarrow, rectangularly shaped, light spot is focused by the light source37 and directed toward the bottom of the resilient roller 26, as shown.A narrow, rectangular exposure region 4 6 is illuminated by the lightspot, and the region 46 extends along the surface of the roller 26parallel to th axis thereof. Thus, as the motor and gear assembly 56cause the master 16 and film 21 to advance in between the rollers 26 and27, the rollers force them into intimate contact within the region ofillumination thereby providing the desired conditions for exposing(printing) the images from the master 16 onto the film 21. Only aportion of the images on the master, the portion within the exposureregion 46, is being exposed or printed at any given instant of time. Asthe master and film are carried by the rotating rollers through theexposure 46, all the images are printed on the film.

lt should be noted that a large diameter roller 27 prevents theresilient covering 28 from wrinkling due to excessive yielding.Therefore, the exposure region 46 can 6 ciably more force to the roller26. Also, it should be noted that by making the diameter of theresilient roller 26 relatively small, a relatively small roller pressurearea 44 is formed. Thus, the large roller 27 and the small roller 26provide a means of producing a high degree of contact within a workableregion without the use of excessive force.

The light source 37 shown in FIG. 4, being held stationary by suitablemeans (not shown), focuses the narrow, rectangularly shaped, light spottoward the bottom of the roller 26 in the following manner: light raysfrom a suitabley pin-hole source 48 are collimated by a lens 49. Inturn, the collimated rays are stopped down .by a mask 51 having anarrow, rectangularly shaped opening. A lens system 52 focuses thenarrow opening in the mask 51 onto the exposure region 46 after thelight rays are reflected and directed toward the roller 26 by a mirror53, that is held stationary by suitable means (not shown). The lightrays are directed radially by the mirror to the inside surface of theglass wall 36 so that any distortions to the light rays due to the glasswall are minimized. Optimum sizes and spacing between the opticalelements can be readily determined by using known optical principles. ltshould be undestood that the light source 37 could be disposed to directthe light rays through the cylindrical glass wall 36 to a mirror or`mirrors located within the roller 27 to be reflected toward the roller26. Then, the other end of the glass wall 36 could also be enclosed byanother disk, similar to disk 38, to provide greater rigidity.. Theroller 26, since it has a greater diameter at its center than at theends, provides a feature which helps to 1 further ensure that airpockets will not be formed in be tween the emulsion coatings as the filmand master are carried through the exposure region 46. As mentionedbefore, since the roller pressure area 44 is wider at the center than atthe ends, then as the rollers 26 and 2 7 ro- 1 tate, the central portionof the film 21 initially makes i contact with the master 16 before theedge portions. This be made to have a workable width without addingappremotion tends to laterally stretch the film and master preventingthe formation of any minute wrinkles, thereby en- A suring bettercontact as the film and master advance through the rollers. Also, as thefilm advances between the rollers, any trapped air bubbles which -maytend to be formed can be forced toward the edges of the film as well asin front of the roller 26, reducing the probability of forming airpockets which would ruin the resolution. The embodiment of the contactprinter described is useful to make contact prints from a highresolution mas.

ter negative in roll form as may be exposed in an aerial photographycamera. Also, the master 16, if it has suicient flexibility, could 'bewrapped around the cylindrical glass wall 36 so that the micro-images onthe master may be repeatedly printed on the film 21. Various otherembodiments and variations of the present invention are contemplated andwill become apparent to those skilled in the art without departing fromthe spirit and scope of the invention. The invention is not limited tothe exemplary apparatus and procedures described, but

includes all embodiments within the scope of the claims. t

What is claimed is:

l. A photographic contact' printer for contact printing high resolutionimages onto a photographic film from a master negative containing highresolution images, said printer comprising: a resilient roller having alarger diameter at the center than at the ends; a transparent memberdisposed for supporting the master negative so that the photographicfilm can be exposed by light rays transmitted through the masternegative; means for rotating said resilient roller and for forcing saidresilient roller against said transparent member so that, when thephotographic film and master negative are disposed therebetween, saidroller rolls over said photographic film forcing the surface of the filmdirectly under the roller into intimate contact with the masternegative; and means for directing and focusing a light spot toward saidresilient roller and through said transparent member, so as to exposeonly the portion of the film having intimate contact with the masternegative.

2. A photographic contact printer for contactprinting high resolutionimages onto a photographic film from a master negative containing highresolution images, said printer comprising: a resilient roller having alarger diameter at the center than at the ends; a rigid roller hav ing atransparent wall for supporting the master negative so that thephotographic film can be exposed by light rays transmitted through themaster negative; said rollers being mounted to rotate about parallellydisposed axes so that-the surfaces of the rollers roll over each other;means for rotating and for forcing said rollers together so that, whenthe photographic film'and master negative are advanced therebetweem'thesurfaces of the lm and the master negative directly between the rollersare forced into contact; and means for directing and focusing a lightspot toward Athe resilient roller and through said transparent wall tothe region where the film and negative are in contact for exposing onlythe portion of the photographic film in contact with the masternegative.

3. A photographic contact printer for contact printing high resolutionimages onto a photographic film from a master negative containing highresolution images, said printer comprising: a resilient roller having alarger diameter at the centerthan at the ends; a rigid roller having atransparent wall of substantially greater diameter; than said resilientroller; said rollers mounted to rotate about parallelly disposed axes sothat the surfaces of the rollers roll over each other; means forrotating and for forcing said rollers together so that, when thephotographic film and master negative are advanced therebetween, saidresilient roller yields contacting the film within a small area formingintimate contact between the film and negative within a narrow areadisposed at the cen'ter of the small area and parallel to said axes; andmeans for directing an/d focusing a narrow light spot onto the narrowarea to expose the film as the film and master negative advance betweensaid rollers.

4. A photographic contact printer for contact printing high resolutionimages onto a photographic film from a master negative containing highresolution images, said printer comprising: a resilient roller having alarger diameter at the center than at the ends; a rigid roller having atransparent wall for-supporting the master ncgative so that thephotographic film can be exposed by iight rays transmitted through themaster negative; said rollers being mounted to rotate about parallellydisposed axes soA in Contact with the negative.

5. A photographicv contact printer for printing high resolution imagescomprising: a resilient roller having a larger diameter at the centerthan at the ends; a master containing high resolution images; atransparent member disposed for supporting the master; a 'film providedwith a coating of emulsion positioned over said master; means forrotating said resilient roller over said film and for forcing saidresilient roller against said film so that the portion of the film underthe roller is forced into contact with the master; and means fordirecting and focusing a light spot toward said resilient roller andthrough said transparent member and for causing relative movementbetween the light spot and the film as said roller rolls over the filmto expose only the portion of film in contact with the master.

References Cited bythe Examiner UNITEDSTATES PATENTS 2,427,443 9/ 1947Cochran.

3,148,611 9/1964 Eisner et al. 95-7'7.5 3,150,262 9/1964 Ulseth et al.95-77.5 X 3,168,022 2/ 1965 Limberger 95-77.5 X

JULIA E. COINER, Primary Examiner.

1. A PHOTOGRAPHIC CONTACT PRINTER FOR CONTACT PRINTING HIGH RESOLUTIONIMAGES ONTO A PHOTOGRAPHIC FILM FROM A MASTER NEGATIVE CONTAINING HIGHRESOLUTION IMAGES, SAID PRINTER COMPRISING: A RESILIENT ROLLER HAVING ALARGER DIAMETER AT THE CENTER THAN AT THE ENDS; A TRANSPARENT MEMBERDISPOSED FOR SUPPORTING THE MASTER NEGATIVE SO THAT THE PHOTOGRAPHICFILM CAN BE EXPOSED BY LIGHT RAYS TRANSMITTED THROUGH THE MASTERNEGATIVE; MEANS FOR ROTATING SAID RESILIENT ROLLER AND FOR FORCING SAIDRESILIENT ROLLER AGAINST SAID TRANSPARENT MEMBER SO THAT, WHEN THEPHOTOGRAPHIC FILM AND MASTER NEGATIVE ARE DISPOSED THEREBETWEEN, SAIDROLLER ROLLS OVER SAID PHOTOGRAPHIC FILM